SAN FRANCISCO — Apple's iOS 7 launch is fast becoming its most troubled mobile operating system update, increasing concern that the technology giant has lost some of its magic touch since co-founder Steve Jobs passed away two years ago.

Since iOS 7 was released Sept. 18, the list of bugs and flaws has grown.

Draining batteries, dropping Wi-Fi and spotty Bluetooth connections are getting big boos across discussion boards at Apple's own support communities. Some apps are working poorly or slowly, the interface is harder to use for some people, and game players have also found faults.

"Apple really needs to get back to focusing on device testing and hyper attention to detail to maintain customers' trust," says Jefferson Wang, senior partner with IBB Consulting.

Text messaging via iMessage, nearly as indispensable as a phone call, has users fuming over an inability to consistently send text messages from iPhones with the new operating system.

On iMessage, "I'll do the hard restart, and that seems to work, but it's pretty frustrating. It shouldn't happen this way, because everyone uses iMessage," Eric Retzlaff, 33, who works at The Doctors Company in Napa, Calif., said in an interview.

Some users of Apple's new flagship iPhone 5s have even experienced a so-called blue screen of death, familiar to many who have seen a Windows computer screen freeze and turn blue.

"It did feel more like a Microsoft release," Retzlaff said. "I've never had an issue like this with one of their updates, so it's pretty shocking."

Apple's problems raise questions about its dramatic mobile makeover decisions and the company's elevation of Jony Ive to oversee much of that development.

"It's Apple's most problematic operating system launch so far," said Raluca Budiu, senior researcher at consulting firm Nielsen Norman Group, which released a report on Oct. 12 saying the design of the new operating system makes it harder to use.

Buttons that used to stand out now blend with the background, and links that used to be visible may now be mistaken for plain text, the consulting firm said.

Budiu has also experienced problems with iOS 7 personally. When she installed the new OS on her older iPhone, it drained the battery much faster. When she got the latest iPhone 5s, she thought that would fix the issue, but the new phone's battery is still draining quicker, she said.

The battery problem may be caused by iOS 7's ability to have many apps running at the same time. In previous versions of the OS, only one or two apps could run at the same time, limiting battery usage, Budiu noted.

Still, Budiu said iOS 7 problems are not as bad as some of Microsoft's legendarily troubled OS upgrades, such as Vista in early 2007. Microsoft's more recent Windows 8 launch was also more problematic, she noted. Microsoft on Thursday began rolling out a Windows 8.1 update to address some user issues.

"iOS 7 is doing some harm but not at the level of Windows 8," she said.

Apple has already released iOS 7 updates to fix some problems, including a bug that allowed people to bypass the Lock screen passcode. But the pace of updates for iOS 7 — two in eight days — is unprecedented for Apple, says Wang. Normally, updates come after 30 to 60 days of a new version of the mobile operating system, he says.

The company is planning more fixes in coming weeks, possibly after an Oct. 22 event at which it is expected to unveil new iPads.

"We are aware of an issue that affects a fraction of a percent of our iMessage users, and we will have a fix available in an upcoming software update," Apple spokeswoman Trudy Miller said. "We apologize for any inconvenience this causes impacted users." She declined to comment further.

HIGH BAR

Some Apple partners said iOS 7 is being criticized so much because the company has trained users to expect its devices and software to work almost magically together with little learning required.

"We expect fantastically high-quality software that automatically works with the hardware. So when these problems come out it seems like the world is ending when in fact it just has a few bugs," said Kiran Bellubbi, CEO of Applauze, an iOS app for concerts, sports and theater tickets.

Indeed, iOS 7 has already been installed on more than 70% of all existing iPhones, iPads and iPod Touches less than a month after launch. Yet there's still an unusually wary group of people who aren't interested in downloading this version.

"In previous iOS releases people have always said, 'Did you get the new iOS?' There's a sizable base that has said, 'We don't like it. We won't download it. We don't want it,'" Wang says.

DESIGN WOES

Apple's iOS 7 mobile operating system iteration took a radical leap from iOS 6. Before it was even launched, those in the design world were sharply divided over Apple's plans to flatten its look.

Apple's move to do away with such design cues as yellow legal pads for Notes, fake glass and other faux vintage effects to resemble objects did away with what's known as skeuomorphism.

"Overall I like the functionality of the new OS, but the visual style looks unfinished. The color design is awful, and it's flat to a fault.," said Mark Rolston, chief creative officer at Frog Design, whose firm designed early Macintosh computers.

Hardware issues are also cropping up. Some Apple users are complaining that the iPhone 5s motion sensors are not working properly. Games that rely on the accelerometer are affected by the apparent flaw, yielding inaccurate results when tilting devices for movement. The new inclinometer and gyroscope used in iOS 7 also are giving flawed results, according to multiple accounts.